The present invention refers to a specifically intended arrangement and a related utilization process, which are adapted to enable moulds to be changed in a very short time in injection moulding machines in which the half-moulds move in an either vertical or horizontal direction relative to each other.
In particular, the present invention applies in a preferred manner to machines adapted for moulding at the same time a plurality of plastic articles, ie. the so-called “preforms”, are intended for subsequent processing by blow moulding into appropriate final containers, especially plastic bottles.
Although reference will be made in the following description, mainly for reasons of greater descriptive convenience, to a machine for moulding preforms of plastic material of the vertical-drive type, as this is used in combination with the preliminary steps of melting and extrusion of the plastic material, it will be appreciated that the present invention shall be understood as applying also to horizontal-drive injection moulding machines or even other kinds of uses or applications, as far as these fall within the scope of the appended claims.
It is generally known in the art that, during the preform moulding operation, use is generally made of a moulding machine comprising a stationary half-mould, which is firmly joined to the structure of the same machine, and a moving half-mould, which moves in a vertical direction and is selectively closable into an appropriate clamped position against said stationary half-mould.
With reference to FIGS. 1A, 1B, 2A, 2B and 2C, which illustrate the state of the art, the upper platen 1, whose particular features shall not be described here since they are already generally known in the art, is associated externally with a moving mould-carrying platen 2, which is in turn connected to the bar 3 that supports the lips 15. The task performed by these lips 15 is to form the neck of a respective bottle and, therefore, they are formed of two separable lip members 15a, 15b in consideration of the fact that, during the removal of the preform from the mould, the neck portion thereof shall be released from its own mould which is formed exactly by the lips. Due to the neck portion being actually provided with a number of undercut-like elements, a selected means for effectively releasing the neck portion from its own mould or lip 15 concerns in making it out of two separable members 15a and 15b, as illustrated in FIG. 7.
To the upper platen there are removably secured, through the use of appropriate fastening means, a plurality of male members 6. Furthermore, to this same upper platen 1 there are firmly associated, in a coaxial arrangement with respect to the male members, respective internal cooling tubes 7.
The mould is completed on the bottom by a cavity-carrying platen 4, in which there can be noticed a plurality of cavities 8 adapted to be filled with the material that is injected through respective nozzles 9.
The coupling of the upper platen 1 with the cavity-carrying platen 8 is brought about by means of a plurality of guide columns 13, which are firmly joined on top to the upper platen 1 and are adapted to slide into insertion in respective through-holes 10 appropriately provided in the cavity-carrying platen.
Furthermore, in view of ensuring the required alignments and the parallelism of the movements, even the moving platen 2 is provided with appropriate through-holes 11 adapted to be slidably engaged by the same guide columns 13.
During the practical operation of the injection moulding machine, it frequently occurs that such operational conditions arise as to make it necessary for access to be gained to the male members in order to replace and/or repair them. As it can most easily be inferred from the illustration in FIGS. 2A, 2B and 2C, when such a need arises for the male members 6 to be replaced and/or repaired, the first thing that must be done is to start by separating the moving mould-carrying platen 2 from the upper platen 1, in such a manner as to create a gap between those platens. Therefore, proper access can be gained manually to the fastening means so as to act on these so as to release and remove the male members 6.
Now, such an operation can actually be carried out in a quite easy and convenient manner if there are just a few (ie. not many) of the male members and these are further arranged in a single row. If on the contrary the male members are arranged in several rows, as illustrated in the Figures, then it becomes much more difficult and awkward for anyone to gain access to the male members due to the limited space that is available for such a purpose, so that the removal and re-assembly operation generally turns out to require a much longer time to be completed.
If the fact is finally taken into due account that, due to production-related or market-driven reasons, the need may actually arise for such male members to be replaced even as frequently as once a day, it can be readily appreciated how each such operation for the replacement of the male members, which may typically last as many as four hours, may on the whole turn out to be extremely expensive and time-wasting.
All these circumstances are largely known to all those skilled in the art, and are recalled here for the sole purpose of more effectively introducing and illustrating the technical context to which the present invention relates.